Extractive separation and recovery of hydrochloric acid and iron values from spent pickle liquor

Abstract

The present study deals with the solvent extraction of hydrochloric acid from spent pickle liquor with two branched chain isomers of tertiary alkyl amine, viz. tri-iso-octyl amine (TiOA) and tris(2-ethylhexyl) amine (TEHA), in absence and presence of di 2-ethylhexyl phosphoric acid (HDEHP) and recovery iron from acid free pickle liquor by solvent extraction with Versatic 10 acid as extractant in kerosene. Extraction of hydrochloric acid increased with the increase in extractant concentration, and the acid extracted into the organic phase appears to be associated with one mole of extractant in each cases. The Mc-Cabe Thiele plot indicated that the complete extraction of acid can be achieved in a single and two stages at a phase ratio of O/A = 2.5:1 and 3:1 with 50% TiOA and TEHA, respectively. Whereas in presence of HDEHP the complete extraction of hydrochloric acid achieved in three stages at phase ratio of O/A=5:1. The acid loaded into TEHA + HDEHP and TiOA + HDEHP could be easily stripped with water, whereas the stripping efficiency of the loaded TiOA and TEHA was poor with water. The reason for easy stripping of acid in presence of HDEHP has also been discussed. From acid free raffinate upto 80% iron was extracted using 30% Versatic 10 acid at a phase ratio of O/A=5:1. McCabe Thiele plot for iron showed that iron can be completely recovered in three stages with 30% Versatic 10 acid at a phase ratio of O/A=3.5:1. Loaded iron in the organic phase was easily stripped with dilute sulfuric acid.